The object of the present invention is a process for the purification of 2,6-diisopropyl phenol.
2,6-diisopropyl phenol, i.e. propofol, is a pharmaceutically important compound which is used in anesthesia. The agent is especially well suited for use in surgical procedures of short duration because of its short halflife. The purity requirements of the agent for intravascular administration are very high, and the aim is a purity which is at least 99.9%.
Propofol is commercially available product. It is made from phenol and propene by Friedel-Crafts-alkylation, whereby in the reaction, besides the desired propofol I ##STR1## small amounts of other isomers and phenol derivatives are formed, the major contaminants being (II) 2,4- and (III) 2,5-diisopropyl phenol, (IV) 2,4,6-triisopropyl phenol, and (V) 1-isopropoxy-2,4-diisopropylbenzene.
The compounds formed in the reaction have previously been separated by fractional distillation, but this is very difficult due to the small differences in the boiling points of the compounds to be separated. Thus, after fractional distillation the product still contains up to 0.5% by weight, but normally not less than 0.3% by weight of the said contaminants, as determined mass spectrometrically. Of the above mentioned impurities, the compound 2,4-diisopropyl phenol (II) constitutes the major part, such as up to 3/4, e.g. from about 1/4 to about 3/4 of the total contaminants.